Ondetti et al. in U.K. Pat. No. 2,045,771 disclose mercaptoacyldipeptides of the formula ##STR3## wherein R.sub.1 is hydrogen, alkanoyl, benzoyl, or forms a symmetrical disulfide, R.sub.2 is hydrogen, alkyl, or phenylalkyl, n is zero or one, and A.sub.1 and A.sub.2 each is an .alpha.-imino or .alpha.-amino acid residue joined through a peptide bond. The compounds possess angiotensin converting enzyme inhibition activity.
Sawayama et al. in U.S. Pat. No. 4,248,883 disclose 1-(3-mercapto-2-methylpropanoyl)prolyl amino acid derivatives of the formula ##STR4## wherein R.sub.2 is hydrogen or lower alkyl, R.sub.3 is hydrogen, phenyl, lower alkyl, or substituted lower alkyl, or R.sub.2 and R.sub.3 join together to complete a heterocyclic ring. These compounds are disclosed as possessing angiotensin converting enzyme inhibition activity.
Gordon et al. in U.S. patent application Ser. No. 442,681 filed Nov. 18, 1982, now U.S. Pat. No. 4,499,079, disclose various carboxy and substituted carboxycycloalkylcarbonyl dipeptides. These compounds are disclosed as possessing angiotensin converting enzyme inhibition activity and depending upon the terminal .alpha.-amino acid also possessing enkephalinase inhibition activity.
Weller et al. in U.S. patent application Ser. No. 446,923 filed Dec. 6, 1982, now U.S. Pat. No. 4,456,595, disclose various carboxy and substituted carboxyarylcarbonyl dipeptides. These compounds are disclosed as possessing angiotensin converting enzyme inhibition activity and depending upon the terminal .alpha.-amino acid also possessing enkephalinase inhibition activity.